1. Field of the Invention
The invention relates to synthetically generated displays for aircraft pilots, and more particularly to integrated displays which provide the pilot with aircraft altitude information and the like.
2. Description of the Prior Art
In the use of electronic display systems for aircraft instrumentation, which may replace 10 or more conventional mechanical indicators, it has become increasingly important to devise methods for presenting the information to the flight crew in a clear, uncluttered manner. As the quantity and the complexity of the symbology placed on an indicator increases, the risk of misinterpretation of data due to visual clutter and overlapping symbology becomes significant.
In order for the pilot to maintain or achieve a desired altitude, it is necessary to display accurate information as to actual altitude of the aircraft and command information indicating the altitude to be effected to achieve the optimum flight situation.
In providing such a display, problems arise in allowing the pilot readily to maintain the desired altitude. For ease of operation, the pilot should be able to determine at a glance whether the aircraft has deviated from the desired altitude, which is usually a multiple of 500 feet or an altitude as selected on the control panel and indicated by a "bug." As shown in FIG. 1, which is representative of a typical prior art integrated flight instrument display, it is difficult to determine whether there has been a change in altitude, or indeed if the desired altitude was reached, without a close reading of the display. Thus, an altitude scale or tape 10 represents barometric altitude in increments of 200 feet from about 2,500 feet to 7,000 feet. A digital readout of radar altitude is presented at the bottom center 12 of the display, with a range up to 3,000 feet. In the barometric altitude region there is not enough resolution on the scale to notice small deviations. Further if rolling digits are used to provide an indication of altitude trend, writing and processing time is substantially increased. The time required for the processor to calculate the image pattern and to store the digital elements in memory is considerable and may impose unacceptable restrictions on the display rate and other required processor tasks. However, the present invention does not preclude the use of rolling digits for displays with adequate processing and writing capability. FIG. 6 shows one such application.
The present invention utilizes an improved tape presentation that provides high resolution and permits ready identification of altitude trends without incurring a penalty in processor requirements or adversely affecting the display update rate. It permits the pilot to tell at a glance that the aircraft has maintained or deviated from the desired altitude. Visual coding of the tape gives the pilot the same information as the arrow on a conventional round dial--whether or not the aircraft is at a multiple of 500 feet of altitude.
It is, therefore, the general purpose of the present invention to provide a display in which aircraft altitude and deviation are simultaneously displayed and to do so in a manner which is intuitively simple for the pilot to use and interpret and thus enhance pilot efficiency and safety.